U.S. patent application number 14/329136 was filed with the patent office on 2014-11-06 for method and apparatus for setting radio link of terminal in which multiple carriers are integrated in mobile communication system.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Kyeong In JEONG, Jung Soo JUNG, Soeng Hun KIM, Gert Jan VAN LIESHOUT.
Application Number | 20140328162 14/329136 |
Document ID | / |
Family ID | 43992205 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140328162 |
Kind Code |
A1 |
JEONG; Kyeong In ; et
al. |
November 6, 2014 |
METHOD AND APPARATUS FOR SETTING RADIO LINK OF TERMINAL IN WHICH
MULTIPLE CARRIERS ARE INTEGRATED IN MOBILE COMMUNICATION SYSTEM
Abstract
A method and apparatus for configuring a radio link of a
terminal communicating via aggregated carriers including a primary
cell and a secondary cell are provided. The method includes
detecting a Radio Link Failure (RLF) for the secondary cell,
deactivating the secondary cell, and reporting at least one of a
measurement result of the secondary cell and a measurement result
of neighboring cell of the secondary cell to a base station. The
apparatus includes a transceiver for communicating with a base
station, and a controller configured to detect a RLF for the
secondary cell, to deactivate the secondary cell, and to report at
least one of a measurement result of the secondary cell and a
measurement result of neighboring cell of the secondary cell to the
base station.
Inventors: |
JEONG; Kyeong In;
(Hwaseong-si, KR) ; VAN LIESHOUT; Gert Jan;
(Apeldoorn, NL) ; KIM; Soeng Hun; (Suwon-si,
KR) ; JUNG; Jung Soo; (Seongnam-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Family ID: |
43992205 |
Appl. No.: |
14/329136 |
Filed: |
July 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13509360 |
May 11, 2012 |
8817602 |
|
|
PCT/KR2010/007908 |
Nov 10, 2010 |
|
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14329136 |
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Current U.S.
Class: |
370/221 |
Current CPC
Class: |
H04W 24/10 20130101;
H04L 5/001 20130101; H04W 72/0453 20130101; H04L 43/0811 20130101;
H04W 36/08 20130101; H04L 41/0654 20130101; H04L 5/0098 20130101;
H04W 36/28 20130101 |
Class at
Publication: |
370/221 |
International
Class: |
H04L 12/24 20060101
H04L012/24; H04W 24/10 20060101 H04W024/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2009 |
KR |
10-2009-0108751 |
Claims
1. A method for configuring a radio link of a terminal
communicating via aggregated carriers including a primary cell and
a secondary cell, the method comprising: detecting a Radio Link
Failure (RLF) for the secondary cell; deactivating the secondary
cell; and reporting at least one of a measurement result of the
secondary cell and a measurement result of neighboring cell of the
secondary cell to a base station.
2. The method of claim 1, wherein detecting a RLF for the secondary
cell comprising: receiving consecutive out of sync indications via
the secondary cell; starting a first timer corresponding to the
secondary cell in response to the received consecutive out of sync
indications; recovering the secondary cell if consecutive in sync
indications via the secondary cell before the first timer are
expired.
3. The method of claim 1, wherein detecting a RLF for the secondary
cell comprising: receiving consecutive out of sync indications via
the secondary cell; starting a first timer corresponding to the
secondary cell in response to the received consecutive out of sync
indications; and detecting a RLF for the primary cell if the first
timer is expired.
4. The method of claim 1, wherein deactivating the secondary cell
comprising: identifying a measurement result of the primary cell;
and deactivating the secondary cell if the measurement result of
the primary cell is not satisfied a predetermined condition.
5. The method of claim 4, wherein the predetermined condition
comprises at least one of detecting a RLF for the primary cell or
identifying a measurement result of the primary cell below a
threshold value.
6. The method of claim 1, wherein deactivating the secondary cell
comprising: identifying a measurement result of the primary cell;
and starting a second timer corresponding to the secondary cell and
deactivating the secondary cell if the second timer is expired and
the measurement result of the primary cell is satisfied the
predetermined condition.
7. The method of claim 6, further comprising: stopping the second
timer and deactivating the secondary cell if the identified
measurement result of the primary cell is satisfied the
predetermined condition.
8. The method of claim 6, further comprising: searching a suitable
cell if the measurement result of the primary cell is satisfied the
predetermined condition.
9. The method of claim 6, wherein the predetermined condition
comprises at least one of detecting a RLF for the primary cell or
identifying a measurement result of the primary cell below a
threshold value.
10. An apparatus for configuring a radio link of a terminal
communicating via aggregated carriers including a primary cell and
a secondary cell, the apparatus comprising: a transceiver
configured to communicate with a base station; and a controller
configured to detect a Radio Link Failure (RLF) for the secondary
cell, to deactivate the secondary cell, and to report at least one
of a measurement result of the secondary cell and a measurement
result of neighboring cell of the secondary cell to the base
station.
11. The apparatus of claim 10, wherein the controller receives
consecutive out of sync indications via the secondary cell, starts
a first timer corresponding to the secondary cell in response to
the received consecutive out of sync indications, and recovers the
secondary cell if consecutive in sync indications via the secondary
cell before the first timer are expired.
12. The apparatus of claim 10, wherein the controller receives
consecutive out of sync indications via the secondary cell, starts
a first timer corresponding to the secondary cell in response to
the received consecutive out of sync indications, and detects a RLF
for the primary cell if the first timer is expired.
13. The apparatus of claim 10, wherein the controller identifies a
measurement result of the primary cell and deactivates the
secondary cell if the measurement result of the primary cell is not
satisfied a predetermined condition.
14. The apparatus of claim 13, wherein the predetermined condition
comprises at least one of detecting a RLF for the primary cell or
identifying a measurement result of the primary cell below a
threshold value.
15. The apparatus of claim 10, wherein the controller identifies a
measurement result of the primary cell and starts a second timer
corresponding to the secondary cell and deactivating the secondary
cell if the second timer is expired and the measurement result of
the primary cell is satisfied the predetermined condition.
16. The apparatus of claim 15, wherein the controller stops the
second timer and deactivating the secondary cell if the identified
measurement result of the primary cell is satisfied the
predetermined condition.
17. The apparatus of claim 15, wherein the controller searches a
suitable cell if the measurement result of the primary cell is
satisfied the predetermined condition.
18. The apparatus of claim 15, wherein the predetermined condition
comprises at least one of detecting a RLF for the primary cell or
identifying a measurement result of the primary cell below a
threshold value.
Description
PRIORITY
[0001] This is a continuation application of prior U.S. patent
application Ser. No. 13/509,360, filed on May 11, 2012, which is a
National Stage application under 35 U.S.C. .sctn.371 of an
International application filed on Nov. 10, 2010 and assigned
application No. PCT/KR2010/007908, which claims the benefit under
35 U.S.C. .sctn.119(a) of a Korean patent application filed on Nov.
11, 2009 in the Korean Intellectual Property Office and assigned
Serial No. 10-2009-0108751, the entire disclosure of which is
hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a communication apparatus
and method for a mobile communication system and, in particularly,
to a radio link configuration method and apparatus of a terminal
for communicating data with a base station over multiple carriers
aggregated in a mobile communication system.
BACKGROUND
[0003] Mobile communication systems have developed to provide the
subscribers with voice communication services on the move. With the
rapid advance of technologies, the mobile communication systems
have evolved to support high speed data communication services as
well as the standard voice communication services. Recently, as the
next generation mobile communication system of the 3rd Generation
Partnership Project (3GPP), Long Term Evolution (LTE) is under
development. The LTE system is a technology for realizing
high-speed packet-based communication at about 100 Mbps, aiming at
commercialization in around 2010. Meanwhile, unlike the standard
voice service, most of the data services are allocated resources
according to the data amount to be transmitted and channel
condition. Accordingly, in the wireless communication system such
as cellular communication system, it is important to manage
resource allocation based on the resource scheduled for data
transmission, channel condition, and data amount to be transmitted.
This is the fact even in the LTE system, and the base station
scheduler manages and assigns radio resources. More recent studies
have focused on the LTE-Advanced (LTE-A) for improving data rate
with the adaptation of several new techniques. Carrier Aggregation
(CA) is one of these newly introduced techniques. As compared to
the data communication in which a terminal uses one downlink and
one uplink carriers, the terminal supporting CA is capable of
performing data communication over multiple downlink and multiple
uplink carriers.
[0004] Since the conventional radio link failure detection and
recovery procedure has been designed in consideration of the
terminal assigned a single downlink and a signal uplink carriers,
it is impossible to adopt this procedure to the terminal which
transmits and receives data on multiple aggregated uplink and
downlink carriers without modification. There is therefore a need
of defining an operation procedure of the CA-enabled terminal when
per-carrier radio link failure is detected.
[0005] The above information is presented as background information
only to assist with an understanding of the present disclosure. No
determination has been made, and no assertion is made, as to
whether any of the above might be applicable as prior art with
regard to the present disclosure.
SUMMARY
[0006] Aspects of the present disclosure are to address at least
the above-mentioned problems and/or disadvantages and to provide at
least the advantages described below.
[0007] In accordance with an aspect of the present invention, a
method for configuring a radio link of a terminal communicating via
aggregated carriers including a primary cell and a secondary cell
is provided. The method includes detecting a Radio Link Failure
(RLF) for the secondary cell, deactivating the secondary cell, and
reporting at least one of a measurement result of the secondary
cell and a measurement result of neighboring cell of the secondary
cell to a base station.
[0008] In accordance with another aspect of the present invention,
an apparatus for configuring a radio link of a terminal
communicating via aggregated carriers including a primary cell and
a secondary cell is provided. The apparatus includes a transceiver
for communicating with a base station, and a controller configured
to detect a RLF for the secondary cell, to deactivate the secondary
cell, and to report at least one of a measurement result of the
secondary cell and a measurement result of neighboring cell of the
secondary cell to the base station.
[0009] The terminal for communicating data with a base station
through multiple carriers aggregated in a mobile communication
system is capable of performing radio link failure detection and
recovery efficiently. That is, if radio link failure is detected on
a secondary carrier other than the primary carrier among aggregated
carriers and if the radio link is not recovered on the secondary
carrier before expiry of a timer, the User Equipment (UE) does not
perform measurement to discover a cell suitable for receiving the
normal service, resulting in reduction of UE's power waste. If the
probability of the radio link failure is high on the primary
carrier, the UE performs measurement to discover the cell suitable
for receiving the normal service on a secondary carrier so as to
reduce the delay for radio link connection re-establishment when
the radio link failure is detected on the primary carrier
afterward.
[0010] Other aspects, advantages, and salient features of the
disclosure will become apparent to those skilled in the art from
the following detailed description, which, taken in conjunction
with the annexed drawings, discloses various embodiments of the
present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above and other aspects, features, and advantages of
certain embodiments of the present disclosure will be more apparent
from the following description taken in conjunction with the
accompanying drawings, in which:
[0012] FIG. 1 is a diagram illustrating the architecture of a Long
Term Evolution (LTE) system to which the present invention is
applied;
[0013] FIG. 2 is a diagram illustrating a radio link failure
detection and recovery mechanism adopted in a 3rd Generation
Partnership Project (3GPP) LTE system;
[0014] FIG. 3 is a diagram illustrating an exemplary situation of
carrier aggregation in the LTE system to which the present
invention is applied;
[0015] FIG. 4 is a diagram illustrating a radio link failure
detection and recovery method of a Carrier Aggregation (CA)-enabled
User Equipment (UE) according to an embodiment of the present
invention;
[0016] FIG. 5 is a flowchart illustrating a UE procedure according
to an embodiment of the present invention; and
[0017] FIG. 6 is a block diagram illustrating a configuration of a
UE according to an embodiment of the present invention.
[0018] Throughout the drawings, it should be noted that like
reference numbers are used to depict the same or similar elements,
features, and structures.
DETAILED DESCRIPTION
[0019] The following description with reference to the accompanying
drawings is provided to assist in a comprehensive understanding of
various embodiments of the present disclosure as defined by the
claims and their equivalents. It includes various specific details
to assist in that understanding but these are to be regarded as
merely exemplary. Accordingly, those of ordinary skill in the art
will recognize that various changes and modifications of the
various embodiments described herein can be made without departing
from the scope and spirit of the present disclosure. In addition,
descriptions of well-known functions and constructions may be
omitted for clarity and conciseness.
[0020] The terms and words used in the following description and
claims are not limited to the bibliographical meanings, but, are
merely used by the inventor to enable a clear and consistent
understanding of the present disclosure. Accordingly, it should be
apparent to those skilled in the art that the following description
of various embodiments of the present disclosure is provided for
illustration purpose only and not for the purpose of limiting the
present disclosure as defined by the appended claims and their
equivalents.
[0021] It is to be understood that the singular forms "a," "an,"
and "the" include plural referents unless the context clearly
dictates otherwise. Thus, for example, reference to "a component
surface" includes reference to one or more of such surfaces.
[0022] In the following description, the term "primary carrier"
denotes a carrier referenced for security and mobility among the
carriers aggregated for use by a terminal and is interchangeably
used with the term "first carrier." The term "secondary carrier"
denotes at least one carrier other than the primary carrier.
[0023] FIG. 1 is a diagram illustrating the architecture of a Long
Term Evolution (LTE) system to which the present invention is
applied.
[0024] Referring to FIG. 1, the radio access network of the mobile
communication system includes evolved Node Bs (eNBs) 105, 110, 115,
and 120, a Mobility Management Entity (MME) 125, and a
Serving-Gateway (S-GW) 130. The User Equipment (UE) 135 connects to
an external network via eNBs 105, 110, 115, and 120 and the S-GW
130. In FIG. 1, the eNBs 105, 110, 115, and 120 correspond to
legacy node Bs of Universal Mobile Communications System (UMTS).
The eNBs 105, 110, 115, and 120 allow the UE to establish a radio
link and are responsible for complicated functions as compared to
the legacy node B. In the LTE system, all the user traffic
including real time services such as Voice over Internet Protocol
(VoIP) are provided through a shared channel and thus there is a
need of a device which is located in the eNB to schedule data based
on the state information such as UE buffer conditions, power
headroom state, and channel state. Typically, one eNB controls a
plurality of cells. In order to secure the data rate of up to 100
Mbps, the LTE system adopts Orthogonal Frequency Division
Multiplexing (OFDM) as a radio access technology. Also, the LTE
system adopts Adaptive Modulation and Coding (AMC) to determine the
modulation scheme and channel coding rate in adaptation to the
channel condition of the UE. The S-GW 130 is an entity to provide
data bearers so as to establish and release data bearers under the
control of the MME 125. MME 125 is responsible for various control
functions and connected to a plurality of eNBs 105, 110, 115, and
120.
[0025] FIG. 2 is a diagram illustrating a radio link failure
detection and recovery mechanism adopted in a 3rd Generation
Partnership Project (3GPP) LTE system.
[0026] Referring to FIG. 2, the radio link failure detection is
performed in such a way the UE monitors radio channel state to
determine whether the connection to the eNB is broken, and the
radio link recovery is performed in such a way that, when the radio
link failure is detected, the UE waits for radio link recovery to
the serving cell in a predetermined time rather than transitions to
the idle mode immediately and, if the radio link recovery fails in
the predetermined time, discovers a suitable cell for receiving the
normal service among the neighbor cell to perform re-establishment
procedure with the new cell. The normal service and the suitable
cell for receiving the normal service follows the term `normal
service` and `suitable cell` defined in the 3GPP standard 36.304,
and the suitable cell discovery and re-establishment procedure for
receiving the normal service after the radio link failure and
multiple recovery failures follows `RRC connection re-establishment
procedure` defined in the 3GPP standard 36. 331.
[0027] In case that a single downlink carrier is assigned to the
UE, Qin or Qout information is signaled from the Physical layer to
the Radio Resource Control (RRC) layer through Common Reference
Signal (CRS) of the carrier. Qin is signaled when the CRS
measurement result value on the carrier is greater than a
predetermined reference value.sub.--1, and Qout is signaled when
the CRS measurement result value on the carrier is less than a
predetermined reference value.sub.--2. The CRS is the channel for
measurement and channel estimation as defined in the 3GPP standard
36. 211, and the RRC layer is the layer for controlling radio
resource follows the Radio Link Monitoring procedure specified in
the 3GPP standard 36.133.
[0028] That is, if the N310 Qout signals are sent from the physical
layer to the RRC layer in sequence, the UE starts a T310 timer. If
N311 Q1 signals are received from the physical layer in sequence
during the T310 timer period, the UE regards that the connection to
the current serving cell is recovered. The CRS managed by the UE
during the T310 timer period is the signal transmitted in the
serving cell to which the UE has established the RRC connection. If
it fails to receive N311 Qin signals in sequence from the physical
layer before the expiry of the T310 timer, the UE starts the t311
timer and search neighbor cells (including the serving cell) for a
suitable cell for receiving the normal service during the T311
timer period. If a suitable cell for receiving the normal service
is discovered during the T311 timer period, the UE performs RRC
connection re-establishment to the found cell. If the RRC
connection re-establishment is successful, the UE can continue
communication of control signal/data with the reestablished target
cell without necessity of transition to idle mode. If it fails to
discover a suitable cell during the T11 timer period, the UE
transitions to the idle mode upon expiry of the T311 timer. The
values of T310, N 310, T311, and N311 are signaled to the UE and
determined in the ranges specified in the 3GPP standard 36.311, and
the detail of the RRC connection re-establishment procedure follows
the definition of the 3GPP standard 36.311 (RRC Connection
Re-establishment).
[0029] FIG. 3 is a diagram illustrating an exemplary situation of
carrier aggregation in the LTE system to which the present
invention is applied.
[0030] Referring to FIG. 3, typically an eNB can use multiple
carriers transmitted and receive in different frequency bands. For
example, the eNB 305 can be configured to use the carrier 315 with
center frequency f1 and the carrier 310 with center frequency f3.
If carrier aggregation is not supported, the UE 330 has to
transmit/receive data unit one of the carriers 310 and 315.
However, the UE 330 having the carrier aggregation capability can
transmit/receive data using both the carriers 310 and 315. The eNB
can increase the amount of the resource to be allocated to the UE
having the carrier aggregation capability in adaptation to the
channel condition of the UE so as to improve the data rate of the
UE. In case that a cell is configured with one downlink carrier and
one uplink carrier as a conventional concept, the carrier
aggregation can be understood as if the UE communicates data via
multiple cells. With the use of carrier aggregation, the maximum
data rate increases in proportion to the number of aggregated
carriers.
[0031] If the radio link failure detection and recovery procedure
designed for the UE having single downlink carrier capability is
applied to the UE 330 having multiple downlink carrier aggregation
capability, the unnecessarily frequent radio link failure detection
and recovery procedure is likely to cause inefficiency and thus
there is a need of defining efficient radio link failure detection
and recovery procedure for the UE 330 having the multiple downlink
carrier aggregation capability.
[0032] The present invention proposes an efficient radio link
failure detection and recovery method of a UE for receiving the
data transmitted by the eNB through a plurality downlink carriers
aggregated. In the present invention, the procedure begins in the
state where multiple carriers are activated among the aggregated
carriers and the UE has established the radio link on the
respective carriers.
[0033] If radio link failure is detected on one of multiple
secondary downlink carriers excluding the primary carrier
representing a specific cell referenced for security and mobility,
the UE waits for the recovery of the radio link with the serving
cell on the secondary carrier for the timer_1 duration. At this
time, the primary and secondary carriers represent the serving cell
and neighbor cells of the serving cell. If radio link failure is
detected in a serving cell of a different carrier, the UE may
detect the radio link failure on the corresponding carrier. If the
radio link failure is detected, the UE starts the timer_1 to
determine whether the radio link is recovered. If the radio link is
recovered before the expiry of the timer_1, the UE stops the
timer_1.
[0034] If it is failed to recovery the radio link with the serving
cell of other carrier before the expiry of the timer_1, the UE
checks the radio quality of the primary carrier. If the radio
quality of the first carrier does not satisfy a predetermined
level, the terminal starts the timer_2 to discover the neighbor
cells around the serving cell. That is, if the radio quality of a
specific/serving cell of the primary carrier to cause radio link
failure or has caused the radio link failure already, the UE starts
the timer_2 on the carrier, where the timer_1 has expired, to
perform a measurement operation for discovery of the suitable cell
for receiving the normal service among the neighbor cells
(including the serving cell. Here, if the signal indicating that
the CRS measurement value on the first carrier is less than a
predetermined threshold value, i.e. Qout, is detected a
predetermined number of times in sequence, if the time_1 and
timer_2 start on the primary carrier, or if the radio quality of
the primary carrier is less than a predetermined threshold value,
the UE determines that the radio quality of the first carrier does
not fulfill the radio level.
[0035] If the radio quality of the first carrier is recovered
before the expiry of the timer_2, the UE stops the timer_2 and
deactivates the other carrier among the plural carriers.
[0036] At this time, the timer_2 may be ended, when the radio
quality of the specific/serving cell of the primary carrier becomes
good enough not to cause radio link failure, if the timer_1 starts
on the primary carrier and the radio link is recovered in the
specific/serving cell before the expiry of the timer_1, or if the
timer_2 starts on the primary carrier and a suitable cell for
receiving the normal service is discovered among the neighbor cells
(including the serving cell). If the timer_2 is stopped, the UE
reports the radio quality information on the neighbor cells
(including serving cell) of the secondary carrier to the eNB (when
the neighbor cell having good radio quality is discovered on the
secondary carriers) or deactivates the secondary carrier and
regards that the carrier is not one of the aggregated ones (when no
neighbor cell having good radio quality is detected on the
carrier).
[0037] Meanwhile, if the radio quality of the primary carrier
fulfills a predetermined radio quality at the time point when the
timer_1 has expired on a secondary carrier but not the primary
carrier, the UE deactivates the secondary carrier among the
multiple carriers. That is, if the radio quality of the
specific/serving cell of the primary carrier is good enough so as
not to cause radio link failure, the UE deactivates the secondary
carrier on which the timer_1 is terminated and regards the carriers
as one of the aggregated carriers.
[0038] The timer_1 and timer_2 may be new timers set to the values
different from those of the timers T310 and T311 described with
reference to FIG. 2 without exclusion of reuse of the timers T310
and T311.
[0039] The above-described operation may be applied when the
secondary carrier on which radio link failure is detected is a
solitary carrier with the exception of the primary carrier in the
aggregation. If multiple secondary carriers exist in the
aggregation with the exception of the primary carrier and if radio
link failure is detected on one of the secondary carriers, the UE
waits for the radio link recovery with the serving cell of the
secondary carrier before the expiry of the timer_1 and, if the
timer_1 expires without radio link recovery, the UE deactivates the
secondary carrier and excludes the carrier from the
aggregation.
[0040] According to the proposed method, if radio link failure is
detected on a secondary carrier but not the primary carrier and if
the radio link is not recovered in the serving cell of the
secondary carrier before the expiry of the timer_1, the UE skips
performing measurement operation for discovering a suitable cell to
receive the normal service, thereby minimizing power waste of the
UE. In case that the probability of radio link failure is high on
the primary carrier, the UE performs measurement operation to
discover a suitable cell for receiving the normal service on the
secondary carrier in advance so as to reduce the delay for the RRC
connection re-establishment when the radio link failure is detected
on the primary carrier afterward.
[0041] FIG. 4 is a diagram illustrating a radio link failure
detection and recovery method of the Carrier Aggregation
(CA)-enabled UE according to an embodiment of the present
invention.
[0042] Referring to FIG. 4, it is assumed that the downlink
carrier_1 401 is the primary carrier including a specific cell
referenced for security and mobility. The downlink carrier_2 is a
secondary carrier aggregated for use by the UE. In this embodiment,
it is assumed that the carrier_1 401 and carrier_2 403 are
aggregated for use by the UE.
[0043] In this embodiment, if N310 Qout signals are issued in
sequence from the physical layer to the RRC layer for the carrier_2
403, the UE starts timer_1 at step 421. Before the expiry of the
timer_1, the UE waits for radio link recovery with the serving cell
on the carrier_2 403 at step 421. The radio link recovery may be
performed in the same way as the radio link recovery procedure with
T310 as described with reference to FIG. 2.
[0044] If the timer_1 expires (i.e. if radio link recovery with the
serving cell fails on the carrier_2 403 before the expiry of the
timer 1), the UE detects the radio link recovery failure at step
441 and checks the radio quality of the carrier_1 401 including the
specific cell responsible for the security and mobility at step
443. If the radio quality of the carrier_1 401 is bad to cause
radio link failure afterward, the UE starts the timer_2. Whether
the radio quality of the carrier_1 401 is bad to cause radio link
failure afterward may be determined depending on the following
conditions:
[0045] i) if N_1 consecutive Qout signals issued from the physical
layer to the RRC layer for the carrier_1 401,
[0046] ii) if the timer_1 or timer_2 starts on the carrier_1 401
(timer_1 starts when N310 consecutive Qout signals are received
from the physical layer on the carrier 401, and the timer_2 starts
when the timer_1 has started but the radio link to the
specific/serving cell is not recovered on the carrier_1 401 before
the expiry of the timer_1 401), and
[0047] iii) the radio measurement result on the carrier_1 401 is
less than a predetermined threshold (THRESHOLD_1). That is, if the
above conditions are fulfilled, the UE starts the timer_2 on the
carrier_2 403.
[0048] The UE searches for a suitable cell for receiving the normal
service (perform measurement and check accessibility to the cell
with the receipt of system information) before the expiry of the
timer_2 at step 451.
[0049] If the radio quality of the carrier_1 401 is improved such
that no radio link failure is detected before the expiry of the
timer_2 on the carrier_2 403 at step 451 or if radio link failure
is detected on the carrier_1 401 but recovered soon, the UE detects
this at step 463 and terminates the timer_2 at step 461. At this
time, the recovery of the radio quality of the carrier_1 401 may be
determined when the following conditions are fulfilled:
[0050] i) N_2 consecutive Qin signals are issued from the physical
layer to the RRC layer,
[0051] ii) the timer_1 or timer_2 running on the carrier_1 401 is
terminated (timer_1 termination occurs when the radio link is
recovered in the specific/serving cell on the carrier_1 401 before
the expiry of the timer_1 (the radio link is recovered when the
N311 consecutive Qin signals are received from the physical layer
as described with reference to FIG. 2), and the timer_2
determination occurs when a suitable cell for receiving the normal
service is discovered before the expiry of the timer_2), and
[0052] iii) the radio measurement result on the carrier_1 401 is
greater than a predetermined threshold_2.
[0053] If the timer_2 is terminated at step 461 or if the timer
expires at step 463, the UE reports the radio quality information
of the neighbor cells (including serving cell) to the eNB (e.g.
when a neighbor cell having good radio quality on the carrier_2) or
deactivates the carrier_2 and excludes the carrier from the
aggregation (e.g. when no neighbor cell having the radio quality
good enough on the carrier_2).
[0054] At this time, the timer_1 and timer_2 may be defined as new
timers apart from the T310 and T311 as shown in FIG. 2 but it is
not ruled out to reuse the T310 and 311. Although the description
is directed to the embodiment in which two downlink carriers are
aggregated, the present invention is not limited thereto. That is,
the present invention is applicable as follows:
[0055] 1) when a plurality of secondary carriers exists among the
aggregated carriers and the radio link failure is detected on one
of the secondary carriers other than the primary carrier.
[0056] 2) when the carrier on which the radio link failure is
detected is one secondary carrier other than the primary carrier
(when there are multiple secondary carriers and the radio link
failure is detected on the secondary carrier other than the primary
carrier, the UE waits for the radio link recovery to the serving
cell of the secondary carrier before the expiry of the timer_1; and
if the radio link is not recovered before the expiry of the timer_1
with the serving cell of the secondary carrier, the UE deactivates
the secondary carrier and excludes the secondary carrier from the
aggregation).
[0057] FIG. 5 is a flowchart illustrating the UE procedure
according to an embodiment of the present invention.
[0058] Referring to FIG. 5, the UE detects radio link failure on a
secondary carrier other than the primary carrier among a plurality
of aggregated carriers at step 501. At this time, if N310
consecutive Qout signals are issued from the physical layer, the UE
can detect the radio link failure. Afterward, the UE starts the
timer_1 of the secondary carrier on which the radio link failure is
detected at step 505. At this time, the UE waits for the radio link
recovery in the serving cell of the secondary carrier on which the
radio link failure is detected. If N311 consecutive Qin signals are
issued from the physical layer, the UE determines that the radio
link is recovered in the serving cell of the secondary carrier. If
the timer_1 of the secondary carrier expires (i.e. if the radio
link recovery fails in the serving cell of the secondary carrier
before the expiry of timer_1), the UE detects this at step 511 and
checks the radio quality of the primary carrier at step 521. If the
expiry of the timer_1 of the secondary carrier on which the radio
link failure is detected is not detected at step 511 but the radio
link is recovered in the serving cell of the secondary carrier
before the expiry of the timer_1, the UE terminates the timer_1 of
the secondary carrier at step 515.
[0059] Next, the UE determines whether the radio quality of the
primary carrier is bad enough to cause the radio link failure after
ward or has caused the radio link failure already at step 525
according to the radio link quality check result on the primary
carrier at step 521. At this time, the UE may compare the radio
quality of the primary carrier with a threshold value. For example,
if the radio quality of the primary carrier is less than the
threshold value, the UE may determine that the radio quality of the
primary carrier is bad enough to cause radio link failure afterward
or has caused radio link failure on the primary carrier. If it is
determined that the radio quality of the primary carrier is bad
enough to cause radio link failure afterward or has caused radio
link failure on the primary carrier at step 525, the UE starts the
timer_2 of the secondary carrier, at step 535, on which the radio
link failure has been detected. The UE searches for a suitable cell
for receiving the normal service before the expiry of the timer_2.
This operation includes measurement and cell access check with the
receipt of the system information. Since the determination
conditions for use at step 525 have been described already with
reference to FIG. 4, detailed description thereon is omitted
herein. If the radio quality of the primary carrier does not
satisfy the conditions at step 525, the UE deactivates the
secondary carrier on which the radio link failure has been detected
and excludes the deactivated carrier from the aggregation.
[0060] If the radio quality of the primary goes better or if the
radio link failure has been detected but recovered soon, the UE
detects this at step 541 and terminates the timer_2 of the
secondary carrier on which the radio link failure has been detected
at step 545. Next, the UE deactivates the secondary carrier and/or
reports the measurement result on the neighbor cells of the
secondary carrier (including serving cell) to the eNB at step 549.
Since the exemplary determination conditions available at step 541
have been described with reference to FIG. 4, detailed description
thereon is omitted herein.
[0061] The UE determines whether the timer_1 of the primary carrier
has expired and a suitable cell for receiving the normal service is
discovered during the operation of step 535 at step 551. If a
suitable cell is discovered at step 551, the UE performs RRC
connection re-establishment to the suitable cell at step 555 or
reports the result of step 535 (e.g. the information on the
suitable cell discovered at step 535 or
intra-frequency/inter-frequency/inter-Radio Access Technology
neighbor cell measurement result) to the eNB at step 555. If no
suitable cell is discovered at step 551 and the timer_2 of the
secondary carrier on which the radio link failure has been detected
expires, the UE detects this at step 559 and deactivates the
secondary carrier or reports the neighbor cell (including serving
cell) measurement result on the secondary carrier to the eNB at
step 549.
[0062] FIG. 6 is a block diagram illustrating a configuration of
the UE according to an embodiment of the present invention.
[0063] Referring to FIG. 6, the UE according to this embodiment
includes a transceiver 601, a failure detector 611, a radio quality
checker 621, a timer 631, a recovery executor 641, and search
executer 651.
[0064] The transceiver 601 configures the carrier aggregation of a
plurality carriers for communication with the eNB and radio links
in the mobile communication and communicates data with the eNB. For
this purpose, the transceiver 601 measures CRS and transmits and
receives control information and data. The failure detector 611
uses the CRS measurement value as the input information for
detecting radio link failure and performs radio link failure
detection per carrier in carrier aggregation mode. If the failure
detector 611 detects radio link failure on a secondary carrier
other than the primary carrier, the timer 631 starts trimer_1. The
recovery executer 641 waits for radio link recovery on the
secondary carrier where the radio link failure has been detected
before the expiry of timer_1. If the radio link is recovered in the
serving cell of the secondary carrier before the expiry of the
timer_1, the timer 631 terminates the timer_1. If the radio link is
not recovered in the serving cell of the secondary carrier before
the expiry of the timer_1 of the timer 631, the radio quality
checker 621 checks the radio quality of the primary carrier. If the
radio quality of the primary carrier is greater than a threshold
value, the recovery executor 641 deactivates the secondary carrier
in the aggregation.
[0065] Otherwise, if the radio quality of the primary carrier is
less than the threshold value, the timer 631 starts timer_2 on a
secondary carrier other than the primary carrier where the radio
link failure has been detected or the recovery executor 641
deactivates the secondary carrier immediately without start of
timer_2 and excludes the secondary carrier from the aggregation. If
the timer_2 starts on the secondary carrier, the search executor
651 takes an action for discovery a suitable cell to receive the
normal service. If the radio quality checker 621 detects that the
radio quality of the primary carrier goes better to be greater than
the threshold value or the radio link is recovered from the radio
link failure on the secondary, the timer 631 terminates the
timer_2. If the timer is terminated, the search executor 651 may
terminate the suitable cell discovery operation for receiving the
normal service. If the timer_2 starts on the primary carrier while
discovering a cell suitable for the normal service before the
expiry of the timer_2, the recovery executor 641 performs RRC
connection re-establishment to the suitable cell immediately or
reports the measurement result of the suitable cell discovered
before the expiry of the timer_2 or the neighbor cell to the
eNB.
[0066] That is, the transceiver 601 configures a radio link in one
of serving cells on a plurality of carriers aggregated. If the
failure detector 611 detects radio link failure, the radio quality
checker 621 checks the radio quality of the primary carrier. If
radio link failure is detected, the timer 631 starts timer_1, and
the radio quality checker 621 may determine whether the radio link
is recovered. If the radio link is recovered before the expiry of
the timer_1, the timer 631 terminates the timer_1 and, otherwise,
if the radio link is not discovered, the radio link checker 621 may
check the radio quality of the primary carrier.
[0067] If the radio link checker 621 determines that the radio
quality of the primary carrier does not fulfill a predetermined
radio condition, the timer 631 starts timer_2, and the search
executor 641 searches neighbor cells around the serving cell. If
the radio quality of the primary carrier is recovered before the
expiry of the timer_2, the timer 631 terminates the timer_2, and
the recovery executor 641 controls to deactivate one of the
aggregated carriers. If the radio quality of the primary carrier is
not recovered before the expiry of the timer_2, the recovery
executor 641 controls to configure the radio link in the found
cell. Otherwise, if the radio link checker 621 determines that the
radio quality of the primary carrier fulfills the radio condition,
the recovery executor 641 controls to deactivate one of a plurality
of carriers.
[0068] According to the present invention, the UE is capable of
performing radio link failure discovery and recovery efficiently in
carrier aggregation mode. That is, if radio link failure is
detected on a secondary carrier other than the primary carrier
among aggregated carriers and if the radio link is not recovered on
the secondary carrier before expiry of a timer, the UE does not
perform measurement to discover a cell suitable for receiving the
normal service, resulting in reduction of UE's power waste. If the
probability of the radio link failure is high on the primary
carrier, the UE performs measurement to discover the cell suitable
for receiving the normal service on a secondary carrier so as to
reduce the delay for radio link connection re-establishment when
the radio link failure is detected on the primary carrier
afterward.
[0069] While the present invention has been shown and described
with reference to various embodiments thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the present disclosure as defined by the appended
claims and their equivalents.
* * * * *